Active site residue 297 of Aspergillus niger phytase critically affects the catalytic properties

Citation
A. Tomschy et al., Active site residue 297 of Aspergillus niger phytase critically affects the catalytic properties, FEBS LETTER, 472(2-3), 2000, pp. 169-172
Citations number
21
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
FEBS LETTERS
ISSN journal
0014-5793 → ACNP
Volume
472
Issue
2-3
Year of publication
2000
Pages
169 - 172
Database
ISI
SICI code
0014-5793(20000428)472:2-3<169:ASR2OA>2.0.ZU;2-D
Abstract
The wild-type phytases from the Aspergillus niger strains NRRL 3135 and T21 3 display a three-fold difference in specific activity (103 versus 32 U/mg protein), despite only 12 amino acid differences that are distributed all o ver the sequence of the protein. Of the 12 divergent positions, three are l ocated in or close to the substrate binding site. Site-directed mutagenesis of these residues in A. niger T213 phytase showed that the R297Q mutation (R in T213, Q in NRRL 3135) fully accounts for the differences in catalytic properties observed, Molecular modelling revealed that R297 may directly i nteract with a phosphate group of phytic acid, The fact that this presumed ionic interaction - causing stronger binding of substrates and products - c orrelates with a lower specific activity indicates that product (myo-inosit ol pentakisphosphate) release is the rate-limiting step of the reaction, (C ) 2000 Federation of European Biochemical Societies.